Rebel XSi with a Leica R 400mm f/6.8 Telyt. Shot wide open at f/6.8. Because of the dim lighting and the somewhat slow lens it is shot at an ISO of 1600. 1/250th sec.
This is not the best example shot for this lens but it is currently the best *digital* shot I have. I'll work on getting some more up. The focus setup on this lens allows for very fast manual focus - and it is ideal for birds, planes, or anything else moving fairly quickly or a long way away.
It has some odd features including: it separates into two halves for easy transport. It has a tab that allows the lens to rotate independent from the camera (so if the lens is tripod mounted you can tilt the camera from landscape to portrait). It also has a drop-in filter sleeve. You;d have to see these features in action to really appreciate the oddness.
The bokeh does tend to swirl in some cases but I've noticed that it looks *worse* in the viewfinder than it does in the actual photo. Not sure as to why. Perhaps some viewfinder/lens optics interactions?